This invention relates to a reproducing apparatus with a sub-picture processing function useful in applying to, for example, a DVD (digital versatile disk) video reproducing apparatus.
In techniques related to DVD video systems, video data and management information necessary to reproduce the video data are recorded on an optical disk. A DVD reproducing apparatus reads management data and controls the reproducing position of video data or sets the signal processing mode of a decoder or the like according to the attributes of the video data.
Video data includes main picture data obtained by compressing picture signals by the MPEG (Moving Pictures Experts Group) scheme, audio data obtained by PCM (pulse code modulation) processing audio signals or processing audio signals by the AC-3 system, and further sub-picture data obtained by run-length compressing signals of subtitles or the like. The main picture data, audio data, and sub-picture data are packed and recorded in the form of video packs, audio packs, and sub-picture packs. These packs are put together to form a video object unit (VOBU) to make it convenient to specify a playback range or a playback sequence. Moreover, a management unit called a video object (VOB), a collection of a plurality of VOBUS, is set to make it convenient to select or specify a playback chapter.
Management information includes VOB information to specify the VOB and program chain (PGC) information to determine the order in which a plurality of VOBUs included in the VOB are reproduced. The program chain (PGC) information has cell (Cell) information that specifies one or more VOBUs. Actually, the PGC specifies the order of the Cell. Then, the Cell information has entry information about the VOBUs.
Furthermore, the management information includes information about conditions necessary to decode the sub-picture data. The condition information is actually included in a sub-picture pack. The sub-picture signal has to be displayed in synchronization with the main-picture signal. For this reason, it includes display timing information (or information about the display position and display area on the screen) with respect to the main picture data, display period information, contrast information, and display color information.
As described above, in the DVD system, the display position and display color of the sub-picture signal with respect to the main picture signal have been determined. Thus, the magnitude, color, display position, and the like of the sub-picture signal (subtitles) are realized in the state set by the DVD video producer.
Depending on the users, however, it is desirable that the sub-picture signal (subtitles) should be smaller or larger. Moreover, they may make various requests, such as watermarked display or the change of the display position.